The Florida gunman's AR-15 reportedly jammed during the shooting, and he had 180 more rounds left

Investigators believe the Florida high-school shooting ended earlier than planned because the gunman's AR-15 jammed while he was changing magazines.

The shooter had more than 180 rounds of ammunition left before he fled the scene, CNN reported.

The jammed weapon is one reason why Republican Sen. Marco Rubio said he was reconsidering a ban on high-capacity magazines.

Authorities believe the Florida high-school shooter's weapon jammed when he was changing magazines during the massacre, likely prompting him to flee the scene before he finished his killing spree, CBS Miami reported on Tuesday.

Nikolas Cruz, 19, allegedly killed 17 people at the Marjory Stoneman Douglas High School on February 14, firing nearly 150 shots in just seven minutes.

Investigators believe Cruz had tried to gun down down fleeing students from a makeshift sniper's nest on the third floor of the building, but that hurricane-proof glass in the stairwell window stopped his bullets.

Authorities said Cruz then ditched his weapon and escaped by blending into a crowd of students. The source also told CNN that Cruz had swastikas etched onto the magazines.

Cruz's jammed AR-15 was precisely the reason that Sen. Marco Rubio of Florida said he was changing his position on banning high-capacity magazines. During a CNN town hall last week, Rubio said he believed such legislation could have made the Parkland shooting less deadly.

"I traditionally have not supported looking at magazine clip size, and after this and some of the details i learned about it, I'm reconsidering that position and I'll tell you why," the Republican senator said. "I believe that there will be evidence that at a key moment in this incident, three or four people … might be alive today because of something that this deranged killer did — had to do."